JP-A No. 2002-503168 and JP-A No. 2014-500178 disclose webbing take-up devices equipped with a pretensioner mechanism that causes webbing to be taken up onto a spool by causing the spool to rotate in a take-up direction at the time of a vehicle emergency. In the pretensioner mechanism disclosed in these documents, a moving member that has been moved by the activation of a gas generator becomes engaged with plural teeth disposed an interval apart from each other in the circumferential direction of rotation of the spool, whereby the webbing can be taken up onto the spool.
In this connection, in terms of efficiently transmitting to the spool the kinetic energy of the moving member that has been moved by the activation of the gas generator, inhibiting the moving member from moving in a direction away from the plural teeth when the moving member becomes engaged with the plural teeth is essential.